CMOS image sensor using gradient index chip scale lenses

Abstract

A camera module includes a gradient index lens on a spacer plate attached over an array of pixel sensors and associated micro lenses. The spacer plate and gradient index lens can be formed at the wafer level during the manufacture of multiple camera modules. A process for manufacturing the camera modules thus provides tolerances and yields provided by wafer processing techniques rather than mechanical assembly.

1. A process for fabricating camera modules, comprising:
 forming a plurality of arrays of pixel sensors on a wafer; 
 attaching a spacer plate to the wafer over the arrays of pixel sensors; 
 forming a plurality of lenses on the spacer plate, wherein each lens corresponds to and overlies one of the arrays of pixel sensors and forms an image across an area of the corresponding array of pixel sensors; and 
 splitting the wafer to separate camera modules, each camera module including one of the arrays of pixel sensors and one of the lenses, 
 wherein the step of forming the plurality of lenses on the spacer plate is performed after the step of attaching the spacer plate to the wafer, and further including: 
 forming a plurality of arrays of micro lenses, wherein the micro lenses focus light onto corresponding pixel sensors: 
 wherein forming the arrays of micro lenses comprises forming arrays of gradient index micro lenses in a lens layer having an upper surface that is substantially flat, the upper surface of the lens layer is an upper surface of the micro lenses, and attachina the spacer plate includes attaching the spacer plate directly to the upper surface of the micro lenses. 
 
     
     
       2. The process of  claim 1 , wherein each of the lenses comprises a gradient index lens. 
     
     
       3. The process of  claim 1 , wherein attaching the spacer plate comprises attaching the spacer plate to the arrays of micro lenses. 
     
     
       4. The method of  claim 1 , wherein attaching the spacer plate comprises directly attaching the spacer plate to the upper surface of the lens layer. 
     
     
       5. The process of  claim 1 , further comprising forming notches in the spacer plate before attaching the spacer plate to the wafer, wherein the lenses are formed on a side of the spacer plate opposite to the notches. 
     
     
       6. The process of  claim 5 , further comprising separating portions of the spacer plate along the notches after forming the lenses. 
     
     
       7. The process of  claim 6 , wherein separating the portions of the spacer plate comprises cutting the spacer plate down to the notches. 
     
     
       8. The process of  claim 6 , wherein the wafer comprises electrical contacts that underlie the notches and are exposed when the portions of the spacer plate are separated. 
     
     
       9. The method of  claim 1 , further comprising forming a patterned layer that defines apertures of the camera modules. 
     
     
       10. The method of  claim 9 , wherein the patterned layer overlies the lenses. 
     
     
       11. The process of  claim 1 , wherein attaching the spacer plate includes facing a first surface of the spacer plate toward the arrays of pixel sensors, and
 forming the plurality of lenses includes forming the lenses on a second surface of the spacer plate that is disposed opposite the first surface, and the second surface is further away than the first surface from the arrays of pixel sensors.